The reaction by which a silicon hydride compound having an Si-H group is added to an alkenyl group (C-C unsaturated bond) is commonly known as hydrosilylation.
The major problem known in the technical field utilizing this reaction is that, under respective reaction conditions, the rate of hydrosilylation reaction drops or the reaction stops in the course of reaction due to the decrease in the activity of the catalyst used during the reaction, for instance. The decrease in the reaction rate not only leads to a protracted reaction time but also results in an increase in the proportion of side reactions to lower the selectivity for the objective hydrosilylation reaction. The reaction may be accelerated by raising the addition amount of the expensive metal catalyst but the practice results in an increase in the amount of catalyst residues in the reaction product, which is sometimes objectionable for subsequent use of the product (taking the hydrosilylation of a high polymer as an example, the black particles derived from the catalyst can hardly be removed so that the product suffers from blackish opacification).
Various methods are known for accelerating a hydrosilylation reaction. For example, as described by Onopchenko, A. et al. [J. Org. Chem., 52, 4118, 1987 and Lewis, L. N. et al. [J. Am. Chem. Soc., 112, 5998, 1990 or in Japanese Kokai Publication Hei-5-213972 and Japanese Kokai Publication Hei-8-283339, the technology of using oxygen for reactivating a deactivated platinum catalyst is known. With regard to substances effective in accelerating the reaction, the technology using an acetylene alcohol (Japanese Kokai Publication Hei-8-231563), an unsaturated secondary/tertiary alcohol system (Japanese Kokai Publication Hei-8-291181), a tertiary alcohol (Japanese Kokai Publication Hei-8-333373), an unsaturated ketone (Japanese Kokai Publication Hei-8-208838) or an ene-yne unsaturated compound (Japanese Kokai Publication Hei-9-25281) is known.
Furthermore, in the system containing elemental N, P, S, Sn or As, which is known as the hydrosilylation catalyst poison, the use of an organoiron compound and/or an organoaluminum compound (Japanese Kokai Publication Hei-6-179821) is also known.
While the rate of hydrosilylation reaction is dependent on reactant species and reaction conditions, the reaction activity is liable to drop particularly in the case that the concentration of unsaturated groups is low, the case that the viscosity of the reaction mixture is high, the case that an internal olefin which is less active than a terminal olefin is involved in the reaction, or the case that the starting material or the solvent contains a reaction inhibitor substance.
Furthermore, there is the tendency that in a system experiencing a drop in reaction activity, a protracted reaction time causes to increase formation of byproducts. The hydrosilylation reaction introducing a hydrolyzable silyl group, such as methoxysilyl, into a polymer is important. A polymer containing a hydrolyzable silyl group is capable of forming a crosslinked compound of higher molecular weight through intermolecular silanol condensation reaction and such crosslinkable polymers are of great use. If the rate of a hydrosilylation reaction for introducing a hydrolyzable silyl group into a polymer drops, the density of crosslinking sites is decreased so that the strength of the crosslinked polymer is ultimately sacrificed.
The technology is k now n which comprises using an expensive noble metal catalyst or a silicon compound in an large amount to improve the reaction yield but it is not acceptable economically. The hitherto-known technology for accelerating a hydrosilylation reaction is, thus, not impeccable but is of ten incapable of solving the problem to a fully satisfactory extent.